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Maximum energy (Read 244 times)
vashu1
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Maximum energy
Jun 18th, 2019 at 10:50pm
 
What is maximum energy/speed of sling missile below 100 g?

I tried calculating it for record throw "record is 477 m set in 1992" but it looks like shape is important and Magnus effect could help to the thrower so computation would not give definitive result.

In "Chronographs" thread maximum velocity 89 m/s is mentioned and average about 56 m/s.

But "Borovsky et al. The traumatic potential of a projectile shot from a sling" AND "Skov, Eric T. Sling Technology: Towards an understanding of capabilities"
give about 50 m/s maximum.

So that 89 m/s looks like chronograph mistake, I guess. Or could it be that Borovsky and Skov didn't try for record throw?
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vashu1
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Re: Maximum energy
Reply #1 - Jun 18th, 2019 at 11:08pm
 
Wiki says fastest pitch ever recorded is 47 m/s(Aroldis_Chapman#Speed_records, with ball weight about 145 g) so I would expect sling record to be much better than 50 m/s.
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Frondeur
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Re: Maximum energy
Reply #2 - Jun 19th, 2019 at 8:53am
 
A guy named Volound claims more than 100m/s on youtube...
https://youtu.be/eoN4EPpCJtQ

Honestly, I don't know what to think of this. I guess his estimations are based on video analysis, but he doesn't give much explanations. I'm not competent enough to contest his numbers, but they are so huge I can't give them credit without any sort of verifications.

If I remember well, Timpa made a radar mesurement at 206 km/h, but I could'nt find the video.

Regarding Borovsky paper, I couldnt find an access to it. is it possible to share a copy?

And by the way, welcome here. I seldom read through the intro part of the forum. Apologize for being such a rude person. Roll Eyes
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TheJackinati
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Re: Maximum energy
Reply #3 - Jun 19th, 2019 at 3:01pm
 
I'd say it's possible to reach 100 m/s. With the very thin Dyneema strands and the long size of the slings that he tends to use, it should be possible.

That said I'd believe velocities of around 70-80 m/s would probably be more average. This is already pretty damned amazing, given that most elite slingers of the Ancient era would probably be attaining maximum velocities of around 60-70 m/s with lead glandes. With modern fibres, I'd believe it is possible to reach or slightly exceed 100 m/s with a good throw.

Of course, the only way to verify this is if they make an attempt for the Guiness World Records.
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Mersa
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Re: Maximum energy
Reply #4 - Jun 19th, 2019 at 7:18pm
 
I think that an average person can learn to use a sling and easily hit 30m/s .
As the sling length gets longer and longer more resistance is put on the sling cords. Deflecting a taught string is much easier than pulling it taught. Think of a guitar string it's under loads of tension but you can easily move the string side to side. Same kind of thing happens with long slings , the trade off is that as the sling gets longer the projectiles mass must get heavier to cancel out the resistance .

I think that a good thrower (fit young tall athlete) that learnt the technique of slinging can easily get to 50m/s.

A very proficient slinger can get a lot more effect from a sling than a person who is starting or learning.
Using long slings is different to shorter slings .
I would think that some advantage comes from a projectile that can get backspin or some other areodynamic effect that creates lift.

I'm confident that a throw on the right day by the right person with the right sling and ammo could hit the 500m mark with a projectile under 100g
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vashu1
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Re: Maximum energy
Reply #5 - Jun 19th, 2019 at 8:48pm
 
Frondeur wrote on Jun 19th, 2019 at 8:53am:
Regarding Borovsky paper, I couldnt find an access to it. is it possible to share a copy?


sure - https://www.dropbox.com/s/bcbkl4eukqwvxxr/Borovsky%2C%20I.%282017%29.%20The%20tr...
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vashu1
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Re: Maximum energy
Reply #6 - Jun 19th, 2019 at 9:03pm
 
TheJackinati wrote on Jun 19th, 2019 at 3:01pm:
With the very thin Dyneema strands


Hm. Here just a rope is used for record throw http://slinging.org/forum/YaBB.pl?num=1117439014

Cross-section of 30 mm stone would be 700 mm^2, 1 meter long double rope with 4-5 mm would be 8-10,000 mm^2 - order of magnitude more(and most of rope moves slower than ball).

I calculated loss of speed for a ball on first meter of flight with https://vashu11.livejournal.com/965.html and got

Cd=0.483325 Distance: 0.0(0.0 ya) Speed: 100.0(328.0 ft/s) Energy: 255.0  Height=1.0
Cd=0.483249960568 Distance: 1.0(1.0 ya) Speed: 100.0(326.0 ft/s) Energy: 253.0  Height=2.0
Cd=0.483174939635 Distance: 2.0(2.0 ya) Speed: 99.0(325.0 ft/s) Energy: 250.0  Height=2.0
Cd=0.483099945407 Distance: 3.0(3.0 ya) Speed: 99.0(323.0 ft/s) Energy: 248.0  Height=3.0
Cd=0.483025618365 Distance: 4.0(4.0 ya) Speed: 98.0(322.0 ft/s) Energy: 246.0  Height=3.0
Cd=0.482951322674 Distance: 5.0(5.0 ya) Speed: 98.0(320.0 ft/s) Energy: 243.0  Height=4.0
Cd=0.482877687411 Distance: 6.0(7.0 ya) Speed: 97.0(319.0 ft/s) Energy: 241.0  Height=4.0
Cd=0.482804087943 Distance: 7.0(8.0 ya) Speed: 97.0(317.0 ft/s) Energy: 239.0  Height=5.0
Cd=0.482731142158 Distance: 8.0(9.0 ya) Speed: 96.0(316.0 ft/s) Energy: 236.0  Height=6.0
Cd=0.482654895462 Distance: 9.0(10.0 ya) Speed: 96.0(314.0 ft/s) Energy: 234.0  Height=6.0
Cd=0.482576856842 Distance: 10.0(11.0 ya) Speed: 95.0(313.0 ft/s) Energy: 232.0  Height=7.0

so we lose 5 m/s per first 10 meter.

From that I feel difference between rope sling and modern one would be 10, 20% at most.
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vashu1
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Re: Maximum energy
Reply #7 - Jun 19th, 2019 at 9:11pm
 
Mersa wrote on Jun 19th, 2019 at 7:18pm:
I would think that some advantage comes from a projectile that can get backspin or some other areodynamic effect that creates lift.


Cool. And I guess there is no way to launch stone(not dart) without spinning?
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TheJackinati
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Re: Maximum energy
Reply #8 - Jun 20th, 2019 at 5:49am
 
Mersa wrote on Jun 19th, 2019 at 7:18pm:
I think that an average person can learn to use a sling and easily hit 30m/s .


Yep. From what I understand this is quite normal for most novice slingers, although I could probably make an exception of 40-50 m/s depending on whether Run-up is involved before a throw, or If a longer sling is used (Though for really large projectiles, ~25-30 m/s is probably more of the norm. Luis Pons Livermore though, with said stones... easily achieves 50 m/s... He's a Human trebuchet!).

On run-ups, I can achieve ~180-200 metres even with horrible limestone, so I definitely think that having a Run-up can cause for high velocities even from a novice... the downside being that... well, You'll be even more of a stormtrooper when slinging!

The average velocity from a standing throw for a novice would probably be around ~30-35 m/s. This is probably where I am at for stones (~60 metres for limestone, ~80-120 metres for clay sphericals), but not for lead. Even when standing with lead projectiles, even with shorter slings I can easily exceed 160 metres.

Mersa wrote on Jun 19th, 2019 at 7:18pm:
I would think that some advantage comes from a projectile that can get backspin or some other areodynamic effect that creates lift.


Well, you can also create a rifling spin as well. Sometimes I twist my wrist slightly just as I go for a throw and this creates rifle spin. Whilst I have no idea whether what I am about to say next is credible... I have a feeling that this would massively reduce the Magnus effect on spherical and ovoid projectiles.

Glandes also seem to want to rifle as well so I don't always twist my wrist when I launch lead. Lead projectiles are marvelous things and all they seem to want to do is FLY! They even like to 'correct' themselves sometimes.
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Frondeur
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Re: Maximum energy
Reply #9 - Jun 20th, 2019 at 1:28pm
 
@vashu1: thanks for the link!

I read it through this afternoon. Well its... creepy.
but worth to understand.
Now, back to wooden targets. Wink
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Re: Maximum energy
Reply #10 - Jun 20th, 2019 at 3:53pm
 
vashu1 wrote on Jun 19th, 2019 at 9:03pm:
TheJackinati wrote on Jun 19th, 2019 at 3:01pm:
With the very thin Dyneema strands


Hm. Here just a rope is used for record throw http://slinging.org/forum/YaBB.pl?num=1117439014

Cross-section of 30 mm stone would be 700 mm^2, 1 meter long double rope with 4-5 mm would be 8-10,000 mm^2 - order of magnitude more(and most of rope moves slower than ball).

I calculated loss of speed for a ball on first meter of flight with https://vashu11.livejournal.com/965.html and got

Cd=0.483325 Distance: 0.0(0.0 ya) Speed: 100.0(328.0 ft/s) Energy: 255.0  Height=1.0
Cd=0.483249960568 Distance: 1.0(1.0 ya) Speed: 100.0(326.0 ft/s) Energy: 253.0  Height=2.0
Cd=0.483174939635 Distance: 2.0(2.0 ya) Speed: 99.0(325.0 ft/s) Energy: 250.0  Height=2.0
Cd=0.483099945407 Distance: 3.0(3.0 ya) Speed: 99.0(323.0 ft/s) Energy: 248.0  Height=3.0
Cd=0.483025618365 Distance: 4.0(4.0 ya) Speed: 98.0(322.0 ft/s) Energy: 246.0  Height=3.0
Cd=0.482951322674 Distance: 5.0(5.0 ya) Speed: 98.0(320.0 ft/s) Energy: 243.0  Height=4.0
Cd=0.482877687411 Distance: 6.0(7.0 ya) Speed: 97.0(319.0 ft/s) Energy: 241.0  Height=4.0
Cd=0.482804087943 Distance: 7.0(8.0 ya) Speed: 97.0(317.0 ft/s) Energy: 239.0  Height=5.0
Cd=0.482731142158 Distance: 8.0(9.0 ya) Speed: 96.0(316.0 ft/s) Energy: 236.0  Height=6.0
Cd=0.482654895462 Distance: 9.0(10.0 ya) Speed: 96.0(314.0 ft/s) Energy: 234.0  Height=6.0
Cd=0.482576856842 Distance: 10.0(11.0 ya) Speed: 95.0(313.0 ft/s) Energy: 232.0  Height=7.0

so we lose 5 m/s per first 10 meter.

From that I feel difference between rope sling and modern one would be 10, 20% at most.


I find it quite unlikely that stones would reach that velocity, at best with a very modern sling, you could probably achieve ~70 m/s throws at max. This would be the upper-limit to what Ancient slingers equipped with lead glandes would have theoretically achieved.

(In the Annabasis for example it cites a range of lead-equipped Rhodian slingers as being around 400 metres, roughly double that of the Persian slingers using fist-sized stones, and largely outranging the Persian archers)

When I was talking about it being possible to achieve 100 m/s throws with a long Dacron-fibre sling, I mean it in reference to Volound's ~52 gram lead projectiles, which are tear-drop shaped airfoils. These are generally being launched from a sling that is probably over two metres in length with a sling that weights around 3 grams.

Also, concerning Borovsky's report, it is probably the best source available yet concerning sling performance. That said I feel that the energy reports are more accurate concerning lower-to-middling range levels of slinging. For example, the stones of 150-200 grams largely maxed out at 30 m/s, Yet an expert like Luis Pons Livermore has been chronographed throwing a 200 gram stone at 52 m/s (Over 200 J), and is known to consistently throw rocks of around ~150 grams at velocities approaching 50 m/s (~180J) even with a fairly short sling (Watermelon from 25 metres video).

But, In general to the answer to your question concerning the maximum energy/speed of a sling missile below 100 g... You'd almost certainly be looking at someone with a ultra high-tech carbon-nanotube fibre sling launching a Osmium, Iridium, Depleted Uranium or Tungsten projectile.

But, until those future slinging mavericks yet-to-be-born arrive, A *lead* projectile is probably going to offer you the most power and range in a 100 gram or less package, which was probably true for the Ancients as well. Using a 42 gram glande from standing with my favourite Jute sling, I can easily reach 200+ metres.

**Unless you want to sling something like Gold, DU or Tungsten, All of which are either extremely expensive, poisonous or very hard to work with... or all three.
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Re: Maximum energy
Reply #11 - Jun 20th, 2019 at 7:56pm
 
There are verified throws of over 500m with lead.

Some quick maths: with idealised projectile (no air resistance)

range = v_init^2 / g
=> v_init = sqrt(g*range)

Plugging the numbers in gives an initial velocity of 70m/s to reach 500m. Note that this is a lower bound, 70m/s would only reach 500m with no air resistance and in reality the launch velocity would have to be higher than 70m/s to reach that range.

Lead is a very good projectile at typical slinging speeds and projectile masses so I would expect the true launch vel for these throws is possibly around 80m/s (i.e. not much higher than the idealised required).

50m/s maximum is for the birds. Experimental archaeologists can only report what they test or observe, but 50m/s gives only ~255m as the theoretical maximum range of the sling (yes, even with lead glandes). This is obviously false given the many verified +250m throws from forum members and the fact that Bray slung a stone (a poor projectile compared to lead) more than 430m.

From what I can see it's pretty much incontestable that multiple people can get around 80m/s launches (assuming the range records are accurate). Additionally I would not be surprised if 90-100m/s launches are also possible, since Larry Bray's 430m+ throw of a stone(!) would arguably put lead out to 700m+, meaning an estimated lower bound of 85m/s and a likely throw velocity of around 95m/s.

Energy of a 95m/s 50g projectile
E = 1/2 *0.05 * 95^2 = 226J
Close to that of a .380 and far surpassing it's momentum due to a much heavier projectile.
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vashu1
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Re: Maximum energy
Reply #12 - Jun 20th, 2019 at 9:50pm
 
JudoP wrote on Jun 20th, 2019 at 7:56pm:
Note that this is a lower bound, 70m/s would only reach 500m with no air resistance and in reality the launch velocity would have to be higher than 70m/s to reach that range.


Yeah. That's what I get with air resistance included

Speed(m/s) = 110
Weight(kg) = 0.054
Cd=0.4848875 Distance: 0.0(0.0 ya) Speed: 110.0(361.0 ft/s) Energy: 331.0  Height=1.0
Cd=0.47961371652 Distance: 100.0(109.0 ya) Speed: 78.0(255.0 ft/s) Energy: 166.0  Height=91.0
Cd=0.475594511043 Distance: 200.0(219.0 ya) Speed: 54.0(179.0 ft/s) Energy: 81.0  Height=155.0
Cd=0.4733287217 Distance: 300.0(328.0 ya) Speed: 41.0(136.0 ft/s) Energy: 47.0  Height=178.0
Cd=0.473472806227 Distance: 400.0(437.0 ya) Speed: 42.0(138.0 ft/s) Energy: 49.0  Height=143.0
Cd=0.475439127447 Distance: 500.0(547.0 ya) Speed: 54.0(176.0 ft/s) Energy: 79.0  Height=22.0
  Range = 512.0 m

So 110 m/s for 500 m.

But Magnus effect makes this calculation useless.  Cry

Simple example - in 19th century(about 1840-50, Prussia and some other "germans") cannonballs with offset center of gravity were used(to make it rotate in controlled direction). If it was loaded in cannon with heavy part upwards then it flew 50% father.

If we assume that "honest" distance is 350 m(and we get +50% due to Magnus) then 75 m/s would be enough even with air resistance.
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Mersa
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Re: Maximum energy
Reply #13 - Jun 21st, 2019 at 3:06am
 
I agree that areodynamics are playing a role. Even if we don't know the exact proportion positive or negitive.
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Re: Maximum energy
Reply #14 - Jun 21st, 2019 at 4:40am
 
Hmmm, very interesting fact about the cannonballs.
I wouldn't actually expect aerodynamic effects to be very large on sling bullets, magnus or otherwise, again just purely on the basis that a lead density projectile of about 50-100g at ~50-100m/s isn't really the right scale (just a hunch though I may try some rough calculations later).

Most of the long range slinging records are set with lead glandes which spin on the axis in the direction of travel (like rifled bullets), so the magnus effect wouldn't be acting  anyway. Also lead glandes presumably travel further than lead balls (given their popularity), so perhaps the magnus effect if it can be achieved is just not strong enough on lead balls to be well utilised?

I know people who sling golf balls can get lift out of them though.
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